Fall In Titer Research Articles

COVID-19 Antibody Response in Patients with Thalassemia.

Background The coronavirus disease 2019 (COVID-19) can severely affect people with comorbidities such as those with diabetes, hypertension, chronic lung disease, cancer, and hemoglobinopathies. Studies assessing the clinical characteristics and immune response to COVID-19 infection in patients with thalassemia are limited. Objectives The primary objective of the study was to study the clinical pattern and the immunoglobulin G (IgG) antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients with transfusion-dependent thalassemia (TDT) compared to patients without thalassemia. The secondary objective wasto study the relationship of COVID-19 severity with IgG antibody titers. Setting, Design, and Participants This case-control study was conducted at a tertiary care hospital between January 2021 and August 2022. A total of 30 patients with TDT (mean age: 12.7 years, SD: 4.7) and 30 patients without thalassemia (mean age: 13.9years, SD: 7) who tested positive for COVID-19 in the preceding six weeks were recruited. Methods Serum samples from the cases and controls were collected after 6, 12, and 24 weeks of COVID-19 infection for IgG antibody estimation using chemiluminescent immunoassay. Outcome variables The primary variable was comparative analysis of antibody levels and clinical profile of COVID-19 in cases and controls. The secondaryvariable was association of the severity of COVID-19 with the antibody titers produced. Results Symptomatic individuals among cases (n=12) were significantly lesser than controls (n=22) (p=0.009). The median IgG titers of cases and controls were comparable at six weeks (p=0.40), but the titers were significantly lower for cases at 12 weeks (p=0.011) and 24 weeks (p=0.006). There was significant fall in titers from 6 to 12 and 24 weeks in both the groups. The titers were not affected by COVID-19 severity and pre-existing comorbidities. Conclusion Patients with TDT manifest with mild or asymptomatic COVID-19 and mount a comparable IgG antibody response to COVID-19 akin to controls. However, this serological response could not sustain over three to six months advocating the need for protection through vaccination.

A study on seroconversion following first & second doses of ChAdOx1 nCoV-19 vaccine in Central Kerala.

Vaccination against COVID-19 induces spike protein-binding IgG antibodies, a robust correlate of protection against COVID-19. This study was undertaken to assess the humoral response after completion of both the doses of ChAdOx1 nCoV vaccine in healthcare workers (HCWs) at a tertiary care health centre in India. A cross-sectional COVID-19 vaccine-induced antibody study was conducted among HCWs. IgG antibodies against spike protein were measured at least 28 days after the first dose and the second dose of vaccination in both SARS CoV-2 naïve and recovered HCWs. Mean and median antibody titre following each dose of vaccine and its association with age, gender, co-morbidities and factors such as exercise, stress and sleep deprivation were also explored. Among the 200 vaccine recipients, 91.5 per cent showed seroconversion after the first dose and 99.5 per cent after the second dose. The mean titre after the second dose was significantly higher when compared to the first dose (12.68±4.17 vs. 9.83±6.3, P=0.001). More than half (54%) had high antibody titre ≥12 S/Co (Signal/cut-off). Previous COVID-19 infection was the single most important factor influencing antibody production, where the mean titre just after a single dose [mean-17.81±5.94, median-20.5 (interquartile range [IQR]-3.7)] surpassed the titre after the second dose in SARS CoV-2 naïve individuals [mean-12.29±4.00, median-12.8 (IQR-3.7), P=0.001]. Furthermore, 28 per cent of vaccinees showed a reduction in titre after the second dose. The mean fall in titre was 2.25±1.40 and was more pronounced in males, the younger age group and those with previous COVID-19 infection. ChAdOx1 nCov-19 vaccine after two doses elicited an excellent immune response. However, greater immunogenicity after the first dose was seen among those with previous COVID-19 infection, even surpassing the titre achieved by the second dose of vaccine in SARS CoV-2 naïve recipients. A fall in antibody titre after the second dose is a matter of concern and requires further studies.

PLA2R and membranous nephropathy: A 3 year prospective Australian study.

The phospholipase A2 receptor (PLA2R) is the major target antigen in idiopathic membranous nephropathy (iMN). The aim of this prospective study was to determine the prevalence of anti-PLA2R in iMN in an Australian cohort. Serum anti-PLA2R was measured using two techniques, an enzyme-linked immunosorbent assay (ELISA) and a cell-based indirect immunofluorescence test. Kidney biopsies were also examined for the presence of PLA2R using a polyclonal antibody. A group of 21 patients with iMN were compared with a group of 19 patients with secondary MN and other glomerular diseases. Seventeen of 21 patients with iMN were positive for anti-PLA2R on both ELISA and indirect immunofluorescence test, and 14 of these patients also had positive staining for PLA2R in the biopsy (tissue was unavailable in two patients). Three patients with iMN had positive staining in the biopsy only, and one patient was negative in both the serum and the biopsy. None of the patients with secondary MN or other glomerular diseases had anti-PLA2R antibodies or PLA2R in the biopsy. There was wide inter-individual variation in titre on ELISA, but serial levels within an individual patient enabled monitoring of disease, and a fall in titre correlated with clinical remission. This is the first Australian series to examine the incidence of anti-PLA2R in iMN. It is also unique in examining sera by two separate techniques in conjunction with tissue localization of PLA2R. We have shown 100% specificity of both serum anti-PLA2R and glomerular PLA2R in iMN, with a sensitivity of 81.0%. When serum testing is combined with tissue localization of PLA2R, the sensitivity increases to 95.2%.

Reactivation of hepatitis B (reverse seroconversion) after melphalan/dexamethasone therapy for primary amyloidosis: a case report

IntroductionHepatitis B virus (HBV) reactivation (so-called reverse seroconversion) is a rare but known complication of hematopoietic stem cell transplantation, immunosuppressive therapy, or high-dose chemotherapy plus rituximab. This event is linked to a treatment-related fall in titers of antibodies to hepatitis B surface antigen (HBsAb) below the protective threshold level.Case presentationA 77-year-old Korean man diagnosed with primary amyloidosis was started on melphalan/dexamethasone combination therapy. During treatment, laboratory indices of hepatic function suddenly deteriorated, and he developed acute hepatitis through reverse HBV seroconversion, becoming positive for hepatitis B surface antigen (HBsAg) and negative for HBsAb. HBV DNA was also detectable in serum to a profound extent. Normal liver function was gradually restored during the course of antiviral therapy (entecavir).ConclusionsHBV reactivation may lead to fatal liver disease in a significant percentage of patients. As a result, physicians often screen for HBsAg and HBsAb prior to initiating chemotherapy, advising antiviral treatment in patients seropositive for HBsAg, even in the absence of hepatitis B e antigen. Here, a case of HBV reactivation is described, involving a patient given relatively low-dose chemotherapy (melphalan/dexamethasone) for primary amyloidosis.

Interaction of Paramecium caudatum and Picornaviruses

In our paper we have researched the relationship between picornaviruses (poliovirus, foot-and-mouth disease virus and encephalomyocarditis virus) and Ciliata (Paramecium caudatum). We show that the number of Paramecium in medium sharply increased during coincubation with picornaviruses within 2-5days. This cannot be explained only by the fact that viruses were nutrient source for Paramecium because in case of inactivated viruses the number of infusorians in medium increased a little. At the same time the titer of viruses harshly decreased whereas in the control group, which is free of Paramecium, the fall of titer was little. Picornaviruses were eliminated from medium if only living Parameciums were present in medium. After 7-9days of coincubation only a few number of viruses were liberated from destroyed Parameciums. These results will be especially useful for management of reservoirs of picornaviruses in water and prevention of diseases.

Serial Kinetics of the Antibody Response against the Complete Brucella melitensis ORFeome in Focal Vertebral Brucellosis

Human brucellosis is a common zoonosis worldwide. Here we present a case of focal vertebral brucellosis in a 71-year-old Mexican-American woman who contracted infection from unpasteurized goat milk. Standard agglutination serology was negative; the diagnosis was established by the isolation of Brucella melitensis from abscess fluid. A B. melitensis protein microarray comprised of nearly all proteins encoded by the bacterial genome was used to determine the kinetics of this patient's antibody responses to the complete collection of open reading frames existing in the genome (ORFeome). Three patterns of antibody responses against B. melitensis antigens were seen for serum samples obtained on days 0 (pretreatment), 14, 49, 100, and 180: (i) stable titers over time, (ii) a steady fall in titers, and (iii) an initial rise in titers followed by declining titers. Sera from this patient with chronic brucellosis recognized some of the same B. melitensis proteins as those recognized by sera from acute/subacute, blood culture-positive brucellosis patients but also recognized a distinct set of proteins. This study is the first to determine the kinetics of the human antibody responses to the complete repertoire of proteins encoded by a bacterial genome and demonstrates fundamentally different immunopathogenetic mechanisms between acute human brucellosis and chronic human brucellosis. While an extension of these findings to a larger patient population is necessary, these findings have important clinical and diagnostic implications and lead toward new insights into the fundamental immunopathogenesis of brucellosis.

The efficacy and tolerability of voriconazole in the treatment of chronic cavitary pulmonary aspergillosis

Voriconazole is the second oral drug licensed for the treatment of aspergillosis. A retrospective non-comparative study was conducted in 16 patients with chronic cavitary pulmonary aspergillosis (CCPA) treated with voriconazole. All patients had failed or were intolerant of itraconazole. The duration of therapy varied from 3 days to 16.5 months. Eleven patients received at least 3 months of therapy with no significant adverse events. Overall seven (64%) patients had a response at 3 months as assessed by at least some fall in inflammatory markers, weight gain and reduction in pulmonary symptoms and two (18%) remained stable. Inflammatory markers improved in 5/11 (46%) with a mean fall in CRP of 0.08 mg/l and ESR of 12.8 mm/h. Aspergillus precipitins were quantitated by numbers of arcs and serum dilution and 11 (100%) showed improvement of at least one band or fall of titre. Total serum IgE was elevated (>200 IU/mL) in 5/11, and fell by a median of 118 kIU/l. Two patients failed therapy. Of the 17 patients, five (27%) had to discontinue therapy as a result of adverse events (three in under 1 week). Adverse events included erythematous rash (5), headaches (4), hepatotoxicity (3), photosensitive rash (3), retinal flashes (3) and neurological symptoms (3). Voriconazole is a useful alternative therapy for CCPA, with a response rate of 64%, over 3 months, and continuing partial remission of disease for much longer periods.

Clinical importance of adenoviral infections

The aim of this article was to point to ubiquitous adenoviral infections and to give a literature overview. Adenoviral infections present with a variety of clinical manifestations, causing many differential diagnosis problems. In our country diagnosis is made using the complement fixation test (CFT), which detects antibodies due to soluble group specific antigen. In acute infections, we need two sera samples given in 2 weeks period with 4-fold rise or fall in titers. Due to many asymptomatic infections which can given increased titer by CFT, many physicians think that patients have a persistent infection. Persistent adenoviral infections need not be accompanied by any special clinical symptomatology. However, adenoviral infections still play an important role in acute respiratory infections. The most severe respiratory infection is pneumonia which can be associated with acute respiratory distress syndrome and death. Disseminated adenoviral diseases appear in 2.5% of all adenoviral infections with the same percentage between immunocompetent and immunocompromised persons. In immunocompromised persons adenoviral infections manifest as haemorrhagic cystitis, fulminant or acute hepatitis or meningoencephalitis. We still don't have a special treatment for these kinds of infections. Variety of antiviral drugs with controversial effects have been reported in management of adenoviral infections in immunocompromised persons. In USA adenoviral vaccine has been excluded from vaccine schedules among military personnel, but morbidity and the first two deaths due to these infections in the last 30 years reported by MMWR in 2000, may change this policy.

High-dose intravenous immune globulin for the treatment of autoimmune blistering diseases: an evaluation of its use in 14 cases.

High-dose intravenous immune globulin (IVIG) is used to treat a wide variety of autoimmune diseases. We report our experiences of its use in a retrospective study of 14 patients with autoimmune blistering diseases, namely epidermolysis bullosa acquisita (EBA), two; bullous pemphigoid (BP), two; pemphigoid gestationis (PG), one; nodular pemphigoid, two; and pemphigus vulgaris (PV), seven. Two patients with refractory EBA improved following regular courses of IVIG given as monotherapy. IVIG had a steroid-sparing effect in 10 patients with PV, BP and PG. However, the clinical effects were transient and of variable intervals, and repeated courses of IVIG were required. The rapid actions of IVIG were of particular benefit in two patients with extensive, rapidly progressive PV and in one patient with BP in whom swift disease control was required. In such cases, when rapid disease control is paramount, we recommend IVIG used in conjunction with conventional treatments as a safer and less invasive alternative to plasmapheresis. IVIG was ineffective in two patients with nodular pemphigoid. Analysis of indirect immunofluorescence (IIF) titres before and after IVIG showed that a fall in titre occurred after 78% of treatments and was observed in all disease groups. However, like the clinical improvements, the falls in IIF titres were transient and of variable interval, and titres rose back to pretreatment levels in all but one patient. IVIG appears to be beneficial under certain circumstances for the treatment of autoimmune blistering diseases but controlled trials are required to define its therapeutic role further.

Use of Bartonella Antigens for Serologic Diagnosis of Cat-scratch Disease at a National Referral Center

Bartonella henselae (formerly the genus Rochalimaea) has recently been isolated from patients with cat-scratch disease and their cats, and since September 1992 the Centers for Disease Control and Prevention has offered an indirect fluorescent antibody assay for Bartonella-specific antibody. Physicians submitted serum samples from patients suspected of having cat-scratch disease or other Bartonella-associated illness and completed a questionnaire that recorded clinical information. Indirect fluorescent antibody assay was performed with the use of antigen derived from three Bartonella species: B henselae, Bartonella quintana, and Bartonella elizabethae. During 16 months, 3088 serum samples were received. The largest numbers of specimens and the highest percentages positive (titer, > or = 64) were observed in the fall and winter. Clinical histories of the first 600 patients for whom serum samples and completed information forms were received were examined in detail; seropositivity was significantly associated with cat contact, cat age of less than 1 year, cat scratch, presence of an inoculation papule, and regional adenopathy. Of 91 patients whose illness met a strict clinical definition of cat-scratch disease, 86 (95%) had titers of 64 or greater to either B henselae or B quintana. A fourfold rise or fall in titer was observed in 87 of 132 patients with paired serum samples. The indirect fluorescent antibody assay for Bartonella-specific antibody is sensitive for the diagnosis of cat-scratch disease. Redefinition of cat-scratch disease on the basis of cause and use of this assay as a diagnostic criterion is recommended.

Frequent and rapid emergence of mutated pre-C sequences in HBV from e-antigen positive carriers who seroconvert to anti-HBe during interferon treatment

Hepatitis B virus (HBV) variants which cannot express e-antigen (HBeAg) are characteristic for many viremic anti-HBe positive chronic carriers who often have particularly severe and fluctuating hepatitis. Whether such variants are selected for and are less amenable to interferon treatment is under dispute. Therefore, by DNA amplification and direct sequencing we have investigated the emergence of HBV pre-C sequence variants in nine e-antigen positive chronic carriers, all of whom seroconverted to anti-HBe or lost HBeAg during interferon treatment, and in three of whom no viral DNA was detectable after interferon treatment. In most, but not all of the patients we found newly emerging pre-C sequences in a subpopulation of the viral genomes that included silent point mutations, amino acid changes, start and stop codon and frameshift mutations. The emergence of these mutations was paralleled by a drastic decrease of viremia during treatment. The observed mutations appeared most frequently during interferon treatment. Some of the mutations appeared or disappeared late after interferon treatment concomitant with anti-HBe antibody development. The appearance or lack of mutations in the pre-C region of a subpopulation of HBV of these patients was independent of successful virus elimination. These data indicate that interferon treatment is frequently associated with the simultaneous fall in titer of viral DNA by several orders of magnitude and the emergence of novel pre-C sequences, some of them preventing HBeAg expression. However, the presumably immune-mediated selection for pre-C mutant viruses and decrease in viremia under interferon treatment appears not to be prognostic for successful or unsuccessful virus elimination.

Persistence of leptospiral agglutinins in Trinidadian survey subjects

Participants in a survey for leptospiral agglutinating antibodies undertaken in Trinidad, West Indies, in 1977-78, were further monitored for up to 5-and-a-half years. 52 individuals with a titre greater than or equal to 1:400 were matched for age, sex and occupation with seronegative subjects. They were re-bled twice (on average 2.38 and 4.84 years later), and changes of titre were noted. At the first follow-up, 78% of negative controls remained negative, and 22%, showed titre changes. Among the seropositive subjects, 47% showed a fall in titre, 38% showed no change, and in 15% the titre rose. New exposure rates between the original and first follow-up samples were 96/1,000 survey population per year in the controls, and 68/1,000 for the subjects with titres greater than or equal to 1:400. Between the first and second follow-up, 47% of the seropositive subjects lost titre, 40% showed no change, and 13% showed a rise in titre. These data demonstrate that although antibody titres may be maintained for a few years at the same level, or show a loss as is usually expected, about 8.3% of individuals in Trinidad may be infected/reinfected per year. The infection/reinfection rate is an important factor in the epidemiology of leptospirosis.

Human ehrlichiosis: prospective active surveillance in febrile hospitalized patients.

Between 1 April 1987 and 30 September 1988 prospective active surveillance of human ehrlichiosis was conducted among febrile patients hospitalized in southeast Georgia. If disease of the immune system, bacterial infection, pneumonia, or surgical illness was documented by the end of the first full day of hospitalization, the patient was excluded. Of 75 patients enrolled in the study, 8 (10.7%) had a fourfold rise or fall in titer to Ehrlichia canis (case-patients). The rate was 5.3 cases/100,000 population. Case-patients were more likely than noncase patients to have become ill in May or June (P = .008) and to report a recent tick bite (P less than .001). At hospital admission, case-patients had lower white blood cell counts (median, 4,450/mm3; P = .001), platelet counts (median, 133,000/mm3 P less than .001), and higher aspartate aminotransferase (median, 68 IU/ml; P = .004) and alanine aminotransferase levels (median, 62 IU/ml; P = .038).

Significance of Freund's adjuvant/antigen injection granuloma in the maintenance of serum antibody response

An experimental system involving injections of ovalbumin (OVA) and ferritin (FER) in Freund's incomplete adjuvant (FIA) into the right and left flank skin folds of sheep was used to study the influence of the FIA/antigen depot and the draining lymph node in maintaining an antibody response. Excision of the injection granuloma and draining lymph node from one side 2–3 months after injections resulted in a profound decrease in serum antibody titres. This response was observed in all eight sheep in the experimental group. In five of eight animals in another experiment, excision of the injection sites had no appreciable effect on antigen-specific antibody titres when compared with antibody specific for antigen on the intact side of the sheep. In the remaining three animals, excision of the injection site did cause some fall in titre. Radiotracer studies revealed that about one-third of the original [ 125I]OVA/FIA injected was present in the granuloma 20 weeks after injection. Lymphatic cannulation approaches were used to study the responsiveness of the lymph node draining an FIA/antigen granuloma established 12 weeks earlier and showed that increments of 1–2 mg OVA in saline administered adjacent to the granuloma at 6–7 day intervals gave rise to strong anti-OVA containing cell (AOCC) responses in lymph. There were 2–6-fold increases in serum antibody titre in response to 3–5 doses of OVA or FER (1–2 mg) in saline injected adjacent to the FIA/antigen injection site (which had been administered 14–16 weeks previously). It is concluded that the release rate of antigen from a FIA/antigen depot is insufficient to sustain maximal antibody levels in blood serum.

Primary and secondary syphilis, 20 years' experience. 3: Diagnosis, treatment, and follow up.

The methods of diagnosis (dark ground microscopy and serology), treatment, and follow up of 946 patients with primary and 854 with secondary syphilis who presented to a London STD clinic between 1965 and 1984 were reviewed retrospectively. On dark ground microscopy spirochaetes typical of Treponema pallidum were seen in 673 (78%) of 884 patients with primary syphilitic chancres. Of the patients with primary syphilis, 137 (14.5%) had negative serology results at presentation. Eight (0.9%) of the patients with secondary syphilis had negative results at presentation, but seven of these gave positive results one month later. Procaine penicillin was the treatment used most, and erythromycin the commonest alternative. The Jarisch-Herxheimer reaction occurred more often after treatment with penicillin than with erythromycin or tetracycline (p less than 0.005). In most patients the Venereal Diseases Research Laboratory (VDRL) test showed a consistent fall in titre after treatment; a small proportion, however, continued to give positive results (some at a high titre) with no other evidence of reinfection or treatment failure.

Should anti‐Rh immunoglobulin be given to D variant women?

D variant women occasionally form anti-D during or following pregnancy with a D-positive fetus. It is not known whether Rh immunization could be suppressed by using anti-Rh immunoglobulin (Rh Ig), or whether the injected antibodies would be absorbed by the woman's D variant cells. In order to predict the likely outcome, three anti-Rh Ig preparations were absorbed independently with five examples of D variant red cells: R1VIr (n = 3), R1Br (n = 2), and with cells of common Rh-positive and Rh-negative phenotypes: R0, r'r, r"r or rr cells (n = 1 each). The titres of the Ig preparations against all these cells were compared after three, six, nine and 12 absorptions. The titres of the unabsorbed anti-Rh Igs against R0 cells ranged from 2(15) to 2(18). Anti-D activities were hardly affected by absorption with r'r, r"r or rr cells, but were completely exhausted after three to six absorptions with R0 cells. Most of the D variant cells were as ineffective as rr cells in reducing anti-D activity against R0 cells, but one R1VIr variant produced a fall in titre against R0 cells, equivalent to four or five doubling dilutions after three to six absorptions, which could not be reduced further by subsequent absorptions. Therefore, a substantial proportion of the anti-D in the immunoglobulin preparation does not bind to D variant red cells. The component of the anti-D that does not bind to D variant cells would be expected to be present in the circulation of D variant individuals injected with anti-Rh immunoglobulin, and should be effective in suppressing Rh immunization. An increased dose of the anti-Rh Ig might have to be administered in order to allow for the fraction that can bind to D variant red cells and which would not be available for immunosuppression.

Coagglutination (COA) test for the rapid diagnosis of cryptococcal meningitis.

Cryptococcus coagglutination (COA) test reagent was prepared locally and showed no cross reactions with different species of bacteria or yeasts or with 75 control sera including 25 that gave positive results for RA factor. We used the COA test to detect cryptococcus antigen in the CSF and we could confirm the diagnosis of 11 out of 115 suspected cases of fungal meningitis; the titre varied from 4 to 128. A four-fold rise in titre confirmed the diagnostic value and a steady fall in titre in three patients on therapy indicated the prognostic value of the test. The earliest confirmation was in a renal transplant patient on the eighth day after onset of symptoms. The COA test was negative with the CSF of 118 patients with chronic meningitis. Cryptococcal colony forming units (cfu) in CSF varied from 100 to greater than 100,000/ml and correlated well with microscopy and with the COA antigen titre in CSF. Four out of the 11 patients who had cryptococcaemia, had 50,000-100,000 cfu/ml in the CSF. Cryptococcus antigen was detected by COA in the serum of all 11 patients, even in those with only 100 cfu/ml in CSF. In the three post-renal transplant patients, who were being monitored regularly, the diagnosis was made early and all three recovered on antifungal therapy with no relapse to date (1-2 years). All the others, including the two primary CNS infections, succumbed to the disease because they presented late for diagnosis and therapy. The cryptococcus COA test is a simple and specific test that can be used as a rapid test to confirm early diagnosis and permit prompt therapy, which should improve the prognosis in CNS and other forms of systemic cryptococcosis. Moreover, it is reproducible and cost-effective, particularly in countries where the latex and other expensive test reagents are not generally available.

Apparent difference in the roles of spleen and lymph nodes in the pathogenesis of host-versus-graft disease in murine parent/F1 chimeras.

Host-versus-graft (HVG) disease is the often fatal immunodeficiency syndrome that can be induced in susceptible strains of mice by the perinatal inoculation of semiallogenic spleen cells. To determine the distribution and engraftment of the donor cells in the spleens and lymph nodes of RFM hosts, sequential tests were done for the presence of (T6 X RFM)F1 cells marked by their ability to form donor-specific antibodies to horseradish peroxidase (HRP) and by the T6 chromosome. Quantitation of cells with intracytoplasmic antibody that bound HRP (HRPBC) and of metaphases with the T6 marker showed that greater than 90% of donor cells were located in the hyperplastic lymph nodes. The pattern of sequential changes in numbers of HRPBC corresponded with the rise and fall in titers of antibodies to HRP. The marked differences in localization of donor cells suggested that host nodes and spleens played different roles. The lymph nodes became the main sources of donor antibodies and the principal repositories of (T6 X RFM)F1 cells capable of replication. The spleen evidently served as a major site of host resistance to engraftment. This was attributed to the ability of host cells there to inhibit selectively the proliferation of the semiallogenic donor cells. It is also proposed that counts of HRPBC measured the vigor of the HVG reaction in host spleen and lymph nodes, because the appearance of virtually all these antibody-forming cells was the result of the maturational effect of the allogenic reaction on F1 donor B memory cells.

Unexplained Febrile Illnesses After Exposure to Ticks

The Ehrlichia are tick-borne rickettsial organisms that cause disease in animals throughout the world but that have been previously recognized as human pathogens only in Asia. We have identified six patients with serological evidence of recent infection with an Ehrlichia: a fourfold or greater rise or fall in titer to Ehrlichia canis. All of the patients reported recent tick bites. Rigors, myalgia, headache, nausea, and anorexia were each reported by five patients. Fever was present in all patients and was accompanied by relative bradycardia and leukopenia in five patients, thrombocytopenia and abnormal liver function test results in four, and anemia in three. Five of the six patients were treated with tetracycline hydrochloride, and all recovered. Infection with Ehrlichia should be considered in patients with unexplained febrile illnesses after tick exposure.

A study of the sero-immunity that has protected the Swedish population against poliomyelitis for 25 years.

Although the population was highly susceptible to poliomyelitis on account of its low natural immunity, the general vaccination with inactivated polio vaccine eliminated poliomyelitis in Sweden within 6 years (1957-62). This status remains after 25 years, although challenges from the introduction of virus occur constantly. Over 99% of the population born in the forties and later is estimated to have been vaccinated, as well as at least 90% of those born earlier. The mean antibody levels of vaccinees against polio range from 100 (type 3) and 500 (type 1) up to 800 (type 2). Seronegative persons are seen only in a small percentage. Evaluation of the duration of immunity indicates that, after the post-vaccination fall in titre which occurs within 2-5 years after immunization, the immune levels remain fairly stable or decline very slowly. Sera from 12-year-old Swedish vaccinees neutralized the type 3 Saukett strain used for vaccine production 5 times better than a type 3 strain isolated during the Finnish outbreak 1984.